Wavelength tunable lasers whose output wavelengths are selectable have been disclosed (see, for example, Patent Literature 1). The technique of Patent Literature 1 stores a control condition for attaining grid wavelengths specified by the ITU-T (International Telecommunication Union Telecommunication Standardization Sector) into a memory and performs control for lasing at any of the grid wavelengths according to thus stored control condition.
Patent Literature 1: Japanese Patent Application Laid-Open Publication No. 2009-026996